Method of applying a conducting coating on insulators



Get. 2,, 1934. Q K, A. HAwLEY A 1,975,576

METHOD OF APPLYING CONDUCTING COATING ON INSULATORS Filed April 7, 1932 dam-mu Patented Oct. 2, 1934 PATENT OFFICE ME'I'IIOD 9F APPLYING A CONDUCTING COATING N INSULATORS Rent A. Hawley, Baltimore, Md., assignor to Locke Insulator Corporation, Baltimore, Md., a corporation of Maryland Application April 7, 1932, Serial No. 603,847

8 Claims.

The invention relates to insulators intended for supporting high tension transmission lines.

In the use of insulators particularly those of that type provided in the head with a conductor receiving groove and also provided with a peripheral groove for the reception of a tie wire for anchoring down the conductor, and also in connection with certain other types of insulators, it has been found that corona forms about the no metal at its juncture or contact with the porcelain or other dielectric material. This corona makes a clearly visible glow when the insulator is viewed in the dark and produces electrical disturbances which are distinctly audible as sputtering noises in radio receivers within a large radius of the insulator. To remedy this objectionable condition it is necessary to eliminate the corona or electrical discharge and various means have been resorted to in this endeavor, such g0 means being sometimes in the natureof adjuncts or attachments to the insulator and in other instances being formed as a part of the insulator itself. Thus far it appears that the most successful remedy has been to provide on the insulator a as conducting coating in good electrical contact with the line conductor and the tie wire and extending over a considerable portion of the area of the insulator. One known method of providing such a coating involves spraying metal onto the porcegm lain surface which must be prepared by sand blasting, a circumstance which renders the method objectionable on account of the expense in production. It has also been proposed to fire the insulator, coat the desired area thereof with 5 a metallic substance such as is used in the decoration of chinaware and then to refire the porcelain to burn in the metal coating. This method is also open to the criticism of being expensive. Mere metallic paints applied to the insulators have also 40 been tried but the permanence of such a coating is extremely doubtful.

It is with the above facts in view that I have devised the present invention which has for its general object the provision of a novel method of applying to the desired area of porcelain insulators a conducting coating of some appropriate or suitable material.

By way of preliminary explanation it might be well to state that in the clays commonly used for 5017116 production of porcelain insulators there is present a certain amount of organic matter left there during its accumulation in the prehistoric swamps. Oxygen actually passes through the pores of this clay mass during the firing operation and burns out these fine particles of organic matter. If thefiring is done too quickly this matter may not be completely consumed and there is left a finely divided carbonaceous residue readily visible on account of its color and called by potters blue core. It is an important object of my invention to take positive steps to prevent the entire burning away of the organic matter so that there will be a definite layer of such carbon residue in the insulator itself at the outer surface thereof where the presence of the carbon will provide electrical conductivity, it being also an object to supplement, if necessary, this carbonized layer with an externallyapplied conducting coating burned into the porcelain during the firing operation.

A more specific object of the invention is to provide a method involving the exclusion of air (oxygen) from the porcelain surface to be made conducting so as to. avoid reduction of the carbon during firing.

A further object of the invention is to provide a method involving the placing in direct physical contact with the porcelain of a substance which in addition to excluding oxygen from the porcelain surface during firing will itself be protected against oxidation and which will be capable of vaporizing or otherwise volatilizing and uniting itself to the porcelain so as to form an integral part thereof and aside from or in conjunction with the carbonized organic matter form a conducting coating, all of this taking place simply during the firing of the clay so that any refiring or other expensive steps will be avoided.

With the above and other objects and advantages in view the invention preferably consists in the method and steps thereof to be hereinafter more fully described and claimed and illustrated in the accompanying drawing wherein:

The figure is a vertical longitudinal sectional view through an insulator part showing a simple means for accomplishing the purpose.

- In the manufacture of insulators it is customary to support the shaped insulators, or insulator sections, depending upon the type, upon what are commonly known as "saggers while they are in the kiln undergoing the firing operation. Such saggers are of. refractory material and are very porous so that there is nothing to interfere with the access of air to the porcelain surface within the confines of the sagger. In the carrying out of my method I contemplate replacing such a sagger with a prefired non-porous I to.

supported upon it in such manner as to provide a substantially airtight joint. In the drawing such a cup is represented at 10 and it will be observed that it supports an insulator 11 in inverted position, the head 12v of the insulator being located within the cup. The cup is intended to be of such size compared with the diameter of the head 12 that its edge will engage" the insulator surface a considerable distance outwardly from or beyond the head. This diameter of the cup with relation to the head depends on the extent of the area desired to be coated. While the cup is represented as supporting the insulator it is of course conceivable that the insulator might be supported by the usual sagger or other means in normal position and the cup 10 arranged in inverted position upon the top of the insulator, it being immaterial which plan is followed except that the first mentioned procedure is probably the simpler.

The insulator with the cup applied thereto either beneath or above it is fired in the kiln in the usual manner and at the customary temperature, the limiting of the amount of air in contact with the porcelain within the confines of the cup preventing reduction of the carbon particles resulting from burning of the organic matter in the clay and the result will be a layer of carbonized matter at and adjacent the surface.

The above may not in some instances result in a sufiiciently continuous conducting layer to accomplish the desired results to the most efiicient extent and as a further refinement in the method, I contemplate filling the cup 10 with some substance 13 which w ll not only exclude substan tially all air (oxygen) from contact with the porcelain but which will itself be capable of forming a conducting coating which will become an integral part of the insulator. Carbonaceous niaterial such as graphite, powdered coal or the like, certain metals, for instance iron filings mixed with carbonaceous material, certain'metallic compounds, for instance silicon carbide, commonly called carborundum and other materials may be used. Whichever one of these or their equivalent, or a combination of such, is placed within the cup will embed the head 12 of the insulator and contact with the adjacent surface thereabout, thereby excluding air from the insulator. Even though air may not be excluded, during the firing a certain amount of the carbonaceous or other conducting material will unite physically with or adhere to the surface of the porcelain and form the desired conductive coating. Particularly if .iron filings form a part of the material within the cup this material will have a chemically reducing effect upon the air inherently present in the pores of the porcelain and will tend to prevent oxidation of the carbonized matter in the clay formed by burning away the organic matter.

After firing has been completed in the usual manner the insulator is used in exactly the same manner as if it were not provided with the coating. However, in actual service an insulator such as the type disclosed is used to support a high tension line conductor seated within the transverse groove 14 in the head 12 and anchored as by a tie wire located within the peripheral groove 15 the conductive coating makes good electrical contact between the conductor and the head and between the tie wire and the surrounding surface and in this way it has been found from actual experimentation and in fact service that corona with the resultant objectionable interference with redio reception is avoided.

ea ers While the method is explained as used in con nection with an insulator of the pin type it should be understood that the same scheme may .be followed out in connection with an insulator of the suspension or cap type where it is desired to establish good electrical contact between the edge of the cap and the porcelain surface either directly or through the medium of an interposed metallic element. However, an insulator of such a variety is not shown and is not described in detail as the method would be the same in either instance.

From the foregoing description and a study of the drawing it is believed that the carrying out of the method, its purpose and its results will be readily understood by one skilled in the art without further explanation.

While I have shown and described a certain means for carrying out the method and have referred to certain substances capable of being used it should be understood that the disclosure is merely an exemplification of the principles involved and that the right is reserved to make all such changes, variations and modifications as will constitute no departure from the spirit of the invention or the scope of the claims hereunto appended.

Having thus described the invention, I claim:

1. In the method of forming a conducting layer in a porcelain insulator, the steps of excluding air from the surface of the unfired porcelain during the firing operation and bringing about a reducing action at said surface to prevent oxidation or combustion of carbon particles naturally present in the clay from which the porcelain is formed.

2. The method of providing a porcelain insulator,with an electrically conductive layer comprising embedding a portion of the insulator in a reducing agent and excluding air from the surface of the unfired porcelain at that area where the layer is desired, and firing the porcelain while so partially embedded.

3. The method of providing a porcelain insulator with an electrically conductive layer comprising covering the surface of the unfired porcelain at the area where the layer is desired with a material capable of excluding air from said surface and acting as a reducing agent, and firing the porcelain while so covered.

4. The method of forming a porcelain insulator with an electrically conductive coating comprising placing the unfired porcelain in a kiln, covering the surface of the insulator where the layer is desired with a carbonaceous material capable of substantially excluding air from said surface and likewise acting as a reducing agent, and firing the porcelain.

5. The method of forming a porcelain insulator with an electrically conductive coating comprising placing the unfired porcelain in a kiln;

covering the surface of the insulator where the layer is desired with granular reducing material capable of substantially excluding air from said surface and also acting to reduce the oxygen content of the air entrapped in said material, and firing the porcelain.

6. The method of forming a porcelain insulator with an electrically conductive coating comprising placing the unfired porcelain in a kiln, covering the surface of the insulator where the layer is desired with an electrically conductive material capable of substantially excluding air from said surface, and firing the porcelain.

"I. The method of providing a porcelain insulator with an electrically conductive layer, comprising placing the unfired porcelain in a kiln and covering the surface where said layer is desired with a substantially pulverulent electrically conductive material capable of excluding air from said surface and also capable of uniting physically with the porcelain at said surface, and firing the porcelain and causing the material immediately contacting said surface to unite perma- 

